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RE: GSBN:Re: Half lime, half cement plaster mix



<x-charset windows-1250>Hi All,

Great comments.

In lime/cement (which we are only using when we have extreme structural
requirements due to unconventional design) we have avoided using soil as a
pigment especially if the desired color is on the darker side of the moon...
The lime is just too strong in whiting/bleaching and gets structurally
compromised by the volume of soil or pigment added.

Our most successful versions of what I assume you are going for are either
structurally tested (in our shop first then at a lab we're seeing 800-2000
psi) cement stabilized earth, called PISE' by some ... and also by fresco
applied modeled pigment.

We also prefer to use hemp fibre in our limes. You need less of it to
minimize cracking and we only have 8 years experience with rice fiber
degrading/graying minimally which is still too short to say its going to
stay that way long term.

Also John is right in pointing out that even a perfect color match in lime
cement doesn't pass for an earth plaster.

Best of luck,

Tim


Tim Owen-Kennedy
Vital Systems Natural Building &amp; Design, Inc.
PO Box 751,  Ukiah, CA  95482
707.468.7488  707.462.3765
www.vitalsystems.net
888.859.6336


-----Original Message-----
From: GSBN [<a  target="_blank" href="mailto:GSBN@...";>mailto:GSBN@...] On Behalf Of Jeff Ruppert
Sent: Wednesday, June 29, 2005 7:05 AM
To: GSBN
Subject: Re: GSBN:Re: Half lime, half cement plaster mix

We have used integral pigment with both pure lime and lime/cement.  The
main thing to look out for is adding too much pigment.  If you are
trying to get a dark, rich color, adding lots of pigment will interfere
with the chemical reaction of the lime and/or cement and weaken it.  If
we are going for a dark color, we apply the pigment by sponge after we
apply the final coat, while it is still wet, and then also paint the
pigment on the next day.  It is a two step process.

If you are concerned about adding too much pigment, you can talk to the
pigment supplier, or even a concrete batch plant operator.  They are
aware of these issues.  They sell pigments and there are specific
maximum ratios of each due to their densities and contents.

Jeff Ruppert, P.E.
Principal

Odisea LLC
Ecological Building, Engineering and Consulting

Front Range Office 		West Slope Office
5444 Marshall Road		1022 Main St.
Boulder, CO  80305		Carbondale, CO 81623
303.443.4335			970.948.5744
303.443.4355 f			1.866.795.6699 f
jeff@...
www.odiseanet.com


MattsMyhrman@...:
> Dear GSBN-ers,
>
> Some friends of mine are considering using the above ratio of lime and
cement
> in their plaster.  They recently asked if I knew of any good reason why
they
> couldn't successfully use standard, commercial plaster pigments to get a
color
> like mud plaster in the final layer (aka, color coat).  I told them I had
> never used pigments in such a mix, but if the pigments consist of various
oxides
> of iron, I didn't think that the higher-than-usual amount of lime in the
mix
> would cause any problems.  If any of you have reason to think that this
was not
> a good answer, I'd sure appreciate hearing from you.
>
> Also, they asked the same question about adding chopped straw to their
mix,
> in order to get a rustic texture.  I told them that I had only used
chopped
> straw in mud plasters and in mud/lime plasters, but that I thought that it
would
> also work fine in the  half lime/half cement mix, assuming that they
didn't
> add so much that it significantly weakened the plaster .  Again, if you
think my
> answer needs adjustment, please share your thoughts.
>
> All best wishes to you all from Judy and myself.
>
> Matts Myhrman / Judy Knox                        mattsmyhrman@...
> Out On  Bale, (un) Ltd.
> 1037 E. Linden
judyknox42@...
> Tucson, AZ  85719
> Office message phone  (520) 622-6896
>
>
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----
GSBN is an invitation-only forum of key individuals and representatives of
regional straw construction organizations. The costs of operating this list
are underwritten by The Last Straw Journal in exchange for use of the GSBN
as an advisory board and technical editing arm.

For instructions on joining, leaving, or otherwise using the GSBN list, send
email to GSBN@...HELP in the SUBJECT line.
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